Water heating solutions: solar water or heat pump?

Choosing the correct renewable energy hot water solution is a difficult decision for many homeowners. In light of all the options and conflicting information available, we have compiled a detailed list of the advantages and disadvantages of solar water heaters and heat pumps, in order for you to make an informed decision.

Advantages: Heat Pump

  • Easy installation: The installation of a heat pump doesn’t require intricate plumbing work and is fairly easy to install, on both a commercial and residential  level.
  • Minimum space requirements: A heat pump needn’t be installed on a roof and it can be installed outdoors.
  • You have hot water 24/7: Because a heat pump relies on electricity, it can provide hot water 24/7 (when there is a dependable electricity supply).
  • Savings: Heat pumps can save up to 50% of energy required to heat water – this translates into a 20 – 30% savings in electricity cost for a household.

Disadvantages: Heat Pump

  • Hard water (water with high levels of calcium carbonate) needs to be treated with a water-softening plant, resulting in the cost going up. Maintenance of the salt levels is vital to ensure the ‘recharging’of the ion exchange.
  • Heat pumps are also noisy and generate the most noise after hot water consumption (At night and early morning). The noise level of a heat pump is measured at 50 decibel.
  • Heat pumps are less efficient than a solar system in high radiation and low ambient temperatures. This makes a solar water heater more ideal for our winters, where we have cold clear skies. A heat pump will lose 50-70% of its efficiency in sub 5 degree temperatures (a heat pump needs heat from the atmosphere to convert cold water to hot water).
  • Heat pumps require a lot of maintenance, due to constant moving parts that needs to be replaced from time to time. Maintenance on a heat pump also requires the skills of a plumber, electrician or aircon technician.
  • The life-cycle of a heat pump is 5-10 years and is completely dependent on electricity to generate hot water.

Advantages: Solar water heater

  • A solar water heater has a 5/10 year factory warranty – depending on the model.
  • The life-cycle of a solar water heater is 10+ years – our oldest system is 11 years old and still running.
  • The quality of the water doesn’t influence the system – a sacrificial magnesium protective anode and double ceramic lined tank prevents corrosion. A solar water heater also handles the issue of calcium carbonate better, as it can be easily scooped out during routine maintenance.
  • The thermostat and element of a solar water heater last longer as it’s only being used 10% of the time.
  • A roof-mounted solar water heater doesn’t rely on electricity to provide hot water when the sun is shining. All systems have a back up element, which means that your household will always have hot water, regardless the weather.
  • There is a variety of solar water heating options available for homeowners who don’t want a solar tank on the roof.
  • The payback period on a solar water heater is low, with a high return on investment.
  • A solar water heater can save up to 90% on water heating cost of a household. This translates to 40 to 50% saving on your total electricity bill.

Disadvantages: Solar water heater

  • High capital upfront investment and installation costs (in comparison to a heat pump in areas with good quality water, otherwise the initial capital costs are the same)
  • A solar water heater works optimally when the sun shines. If it is overcast, the back-up element kicks in to compensate for the lack of solar energy. The back up element will operate approximately 10% of the year.
  • Routine maintenance similar to an electric geyser is needed on a solar water heater, but only on the valves and not on the system itself.

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